The present invention relates to a road or highway expansion joint and in particular to elastic cover strips for sealing the gap between abutting road sections.
Cover strips used for closing the expansion joint of highway or road bed sections are generally known. One such strip (German Pat. No. 25 35 413) is formed of an elastomeric plate having on its underside a pair of open recesses which extend parallel to the center line of the joint and have strengthening ribs running transversely thereto. Reinforcing inserts may also be provided within the strengthening ribs. The ribs serve to distribute the tensional stresses on the one hand and to counteract the upward bulging of the plate in response to the movement of the pavement under compression. By arranging the two spaced recesses, next to each other, so that one overlies the gap between adjacent road sections, the plate area located therebetween is pushed against one section of the concrete base when the cover is placed under compression. However, due to the great forces acting to deform the plate, the ribs are insufficient to assure a continual flat running surface over that portion covering the gap.
In another known arrangement (German Offenlegungschrift No. 1,940,000) an elastomeric plate is anchored to the road bed sections along both its longitudinal side edges under a preloaded transverse tensional force. Aging of the material is accelerated on account of the high material stresses placed on the plate during use. Thus, in the course of time, the elastomeric material creeps apart from the direction of the tensile forces so that the preloaded stress weakens, resulting in the contraction of the elastomeric materials, the plate is then stressed in compression and arches upwardly in the process.
Also known is a cover strip having deep depressions on its top and the bottom surfaces (see German Pat. No. 1,534,377.) When viewed in plan, the depressions have a bow-shape extending transverse to the longitudinal direction of the expansion joint. Despite this, the danger of their buckling out of the plane of the roadbed surface cannot be prevented. This known cover strip, like those described earlier, is formed of rubber without reinforcing inserts and is thus capable of absorbing only relatively small vertical loads.
Another known cover strip having considerably load carrying capacity is shown in U.S. Pat. No. 3,316,574 and German Auslegeschrift No. 2,228,599. These strips utilize plate shaped inserts embedded within the rubber body to bridge the gap between abutting road bed sections. The expansion of the joint is absorbed by the cavities in the rubber body which runs longitudinally laterally adjacent to the gap itself. Since the bridging area of the strip, and the plate-shaped inserts do not function to compensate for material shift caused by the relative movement of the joint, these plate-shaped inserts must be of considerable width in order to be effective.
These disadvantages are overcome by forming a cover strip for road bed expansion joints which retains great elasticity under expansion as well as contraction and has a high load carrying capacity while retaining a stable position avoiding any buckling upward in all states of compression or tension.